1. Field of the Invention
The present invention relates to a vehicle control method and a vehicle control apparatus. Specifically, the present invention relates to a method and an apparatus for controlling a vehicle which can control a tire force, that is, a force generated between a tire and a road surface, by independently controlling each steering angle and braking force of four wheels, and a vehicle which can control a tire force by independently controlling steering angles and braking forces of front wheels and those of rear wheels.
2. Description of the Related Art
A technique for separately controlling four wheels and steering angles thereof has been known, as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2001-322557. According to this related art, when a vehicle turns, the vehicle is steered so that a steering angle of each wheel becomes 90° with respect to the center of the turn of the vehicle. Further, when a defective wheel is found, steering and braking are controlled so that the friction force of the defective wheel is decreased. This related art does not disclose cooperation of steering and braking, or cooperation of steering and driving. For example, regarding the steering angle, a fixed value is outputted as a target value regardless of braking or driving.
However, in an actual vehicle, critical friction is generated between a wheel and a road surface, and lateral force may be decreased by increasing braking force. Therefore, cooperation between steering and braking or between steering and driving is indispensable in order to use the friction force between the wheel and the road surface as efficiently as possible. However, the above related art does not mention the cooperation at all, such as adjusting steering according to braking or driving. As a result, a problem arises in that the force generated by the wheel cannot be optimized.